A conventionally known travel working machine such as a tractor or a wheel loader includes, in a transmission case mounted to a traveling body, a hydraulic mechanical transmission (HMT) for steplessly changing the speed of driving force from the engine by a combination of a planetary gearing and a hydraulic transmission (HST) comprising a hydraulic pump and a hydraulic motor connected to each other via a hydraulic circuit.
An example of such a hydraulic mechanical transmission is disclosed in the patent document described below. In the hydraulic mechanical transmission disclosed in the patent document, the hydraulic pump and the hydraulic motor are combined into one unit.
In the hydraulic mechanical transmission, the pump shaft for input to the hydraulic pump is coaxially connected to the power shaft from the engine. The planetary gearing is provided at the input pump shaft.
The hydraulic motor, which is driven for rotation by the hydraulic pressure generated at the hydraulic pump, is provided below the hydraulic pump. The motor shaft for output from the hydraulic motor is arranged below the input pump shaft to extend in parallel with the input pump shaft. The gear fixed to the output motor shaft meshes with an external gear of the carrier of the planetary gearing which is rotatably fitted to the input pump shaft.
In this case, the lubrication of the planetary gearing is performed by partially or entirely immersing the planetary gearing in the lubricating oil stored in the transmission case.
Patent Document 1: JP-A-2001-108060